In evolved UTRAN (EUTRAN) or other future systems concept, all the traffic across the radio interface takes place on a packet switched basis, i.e., no fixed resource is allocated to any user. In order to provide flexibility and fast allocation of resources, the signalling information in physical layer (L1) has to inform when and where a given user is receiving data in a downlink (or alternatively transmitting information in an uplink).
A number of users registered to EUTRAN under a Node B control can be much larger than that for WCDMA (wideband code division multiple access) systems. This number may be several hundreds of users depending on the bandwidth employed (e.g., 200 active users up to 5 MHz band, and 400 active users for broader spectrum). All of these users need to have an identity assigned to them, i.e. a Radio Link ID or RLID (the term “RLID” can be interpreted broadly; other equivalent terms which may be used instead of RLID may include but are not limited to: a user equipment ID (UEID), a cell radio network temporary identifier (C-RNTI), etc.). Note that the ID for idle users is different from the RLID used for active users (i.e., in an active mode).
Allocations of shared channel resource are done for each L1 subframe. For each subframe, the RLID for each scheduled user, in addition to its transport format information and information indicating where in the subframe its data is located, are signaled. Now, with the number of users being remarkably large, the number of RLIDs needed to signal for one allocation can require significant resources from a total channel capacity. As the allocation information is secondary to the actual traffic being transmitted, the size of this allocation information should be minimized. However, due to the large number of the UEs (user equipments) in the system, the RLID basically has to be at least of the same size as currently in the WCDMA HSDPA (high speed downlink packet access), i.e., 16 bits, for it to be unique for each UE.